[libcxx-commits] [libcxx] [libc++][test] Enhance `ADDITIONAL_COMPILE_FLAGS` to work with MSVC (PR #74974)

[Louis Dionne via libcxx-commits]

https://github.com/ldionne commented:

This makes sense to me and it seems like a reasonable support burden for us. I have a comment, but this looks pretty good to me.

> IMHO, `TEST_CLANG_DIAGNOSTIC_IGNORED`/`TEST_GCC_DIAGNOSTIC_IGNORED`/`TEST_MSVC_DIAGNOSTIC_IGNORED` (from [test_macros.h](https://github.com/llvm/llvm-project/blob/78623b079b3be841e96ce968ae5156fe26f6c565/libcxx/test/support/test_macros.h#L408-L432)) should be the preferred way to disable warnings.

@cpplearner  This is an interesting point. We could also decide to go all out and use the macros instead. TBH I am mostly neutral on this, but I'd be curious to hear what motivates your preference.

https://github.com/llvm/llvm-project/pull/74974